If she ever falls in love, her mate will die in a hundred days.

In “Hungry Heart,” Bruce Springstein sings: “We fell in love, I knew it had to end.” Wait! Hold up there, Boss. Zero to 60 and back, like that? What about love is love and not fade away? Or love not altering when it alteration finds? Real, felt, genuine love should open myriad portals to vistas flecked with gold, not erect a wall.

Eleven years ago, Abigail had a similar reaction. She was listening to Shaun Bengson’s “Massive Anti-Folk-Punk-Old-Timey-Neo-Soul band” rehearse and fell in love with him. She was so struck she abandoned her previous life cold turkey, including her fiancé.

Shaun had a similar reaction. Bells rang, gongs gong’d. They hastened to a diner, where each confessed “you look like forever to me.” She moved in with him on their second date. To make room, Shaun had to evict his brother. When Abigail came on board she still didn’t know Shaun’s last name.

They were married three weeks after they met (when the audience at the La Jolla Playhouse heard this, they let out a glottal, “you WHAT?” groan). Then the other shoe — a studded black cowboy boot, in this case — fell.

When she was 15, Abigail watched her family implode. The trauma was so intense a dream has haunted her ever since: people leave, loved ones die. Harbor your heart. If she ever falls in love, her mate will die in a hundred days.

At the La Jolla Playhouse, 100 lightbulbs overhead and five streams of salt, like the passage of time in an hourglass, turn the fear into indelible images. Ergo: Shaun will be gone in less than four months. Why was Abigail so hasty? Was she hoodwinked by happily ever after? She must face her imagined fact: “I’ve found him and now he’s going to die.”

Shaun has several possible reactions, among them a pronto exit from Dodge. But like Abigail, he’s an introvert with few intimate experiences. And even though the vegan guitarist has programmed himself to be an ascetic (“What would Gandhi do?”), he felt true stirrings and won’t let them, or Abigail, go. Even when she flees in fear after he’s injured in an accident.

In Joseph Heller’s Catch-22, the character of Dunbar is convinced he will die soon. To make his life feel longer, he embraces boredom, and becomes giddy when nothing’s going on. Abigail and the understanding Shaun do the opposite: they vow to fill their 100 days to beyond capacity, live their entire lives in that time, including a trip to the salt flats out West.

Hundred Days is based on a true story. Abigail and Shaun are a talented husband-wife musical duo. She did panic, and he went after her. With explosive material like this — truly felt because true — you might expect an, “aren’t we special,” operatic presentation: Orpheus braves his way down to Hades to resurrect Eurydice, with appropriate bells, whistles, and a Greek chorus of thunderclaps.

One of the many surprises about this show: it’s humble. Backed by four musicians on a multi-leveled bandstand, the Bengsons (their stage name) come across as everyday folks, even self-deprecating. They aren’t narcissistic lab rats eager to extol a great achievement; they’re here to share a story in song with expressive versatility and expert musicianship.

The first ten or so minutes almost feel like a rehearsal. Wearing appropriate attire for an upscale biker bar — black leather jacket and boots, white sequined cocktail dress — Abigail chats with the audience like an old friend. Shaun, in frumpy, retro-neo-mod black suit, looks so shy one wonders if he’s reticent to perform. There’s little fanfare or polish.

Then they perform, the complex sounds emerging as polished as the byplay was not. Ashley Baier grounds the band on drums, as does Reggie D. White on keyboard; Barrie Lobo McLain and El Beh create a mini-sound system on accordion and cello. Abigail plays guitar and floor tom; Shaun, guitar and keyboard. All sing as well. Sixteen songs range from tender lilts to launching rockets. Take all the anti’s in Shaun’s old band (“anti-folk, punk, old-timey, neo-soul”), invert and fuse them, add an occasional Irish inflection, and you might approximate a useful category.

The evening’s biggest song comes when Abigail is on the run. Having given all her heart, she “can’t take any more” and abandons Shaun at the hospital. Engulfed by flaming red lights (designer: Andrew Hungerford), she sings a "dark night of the soul" aria about a three-legged dog like an octave-hopping Janis Joplin. This performance would be stronger if one could make out the words. The band has at least five keyboards. This powerful combination often blurs the lyrics. That’s the one persistent flaw in an otherwise subtle/fierce, surprisingly moving show.

Hundred Days, music and lyrics by the Bengsons, book by the Bengsons and Sarah Gancher.

La Jolla Playhouse, 2910 La Jolla Village Drive.

Directed by Anne Kauffman

Playing through October 21; Tuesday and Wednesday at 7:3 p.m. Thursday through Saturday at 8:00 p.m. Sunday at 7:00 p.m. Matinee Saturday and Sunday at 2:00 pm.